I read this in The Guardian earlier, although I haven't seen the documentary that it talks about. I used to get sleep paralysis on a regular basis, and it could be terrifying at times, although other times it was merely weird, and once or twice funny.
What's interesting, I suppose, is that SP has spawned such a range of folkloric explanations across the world, as well as playing its part in creating the whole alien abduction phenomenon.
I'd be interested to know if anyone knows of any poetry that deals with sleep paralysis - I've written one or two unpublished pieces myself, but it's hard to find the right tone, because however frightening it can be, briefly, it doesn't really have any lasting effects.
Incidentally, I haven't had an episode for about four years - avoiding falling asleep lying on my back seems to have helped, as does simply getting more sleep.